Pain
Pain is an unpleasant sensory and the emotional experience associated with actual or potential tissue damage. It alerts us to danger and tells us when something is wrong within our bodies. If danger is acute the body may react even before the brain is aware of the danger. For example, the reflex action of jumping away from a sharp object or something hot prevents us from being cut or burned. It is only after we have jumped away that we become aware of our actions. Unlike other sensations, the perceptive sensation of pain can be influenced by other past or present experiences, for example, heightened pain perception accompanying fear of needles, or lowered pain perception in an injured athlete during a competitive event. There are three categories of pain receptors: (i) Mechanical nociceptors which respond to mechanical damage such as pinching or cutting. (ii) Thermal nociceptors which respond to temperature extremes. (iii) Polymodal nociceptors which respond equally to all kinds of damaging stimuli. These nociceptors do not have specialized receptor structures, they are all naked nerve endings.
